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cell membrane
biol 1210
| Term | Definition |
|---|---|
| basic structure of cell membrane | bilayer of phospholipids. The hydrophilic heads interact with water while the hydrophobic tails interact with one another |
| lipids do not form polymers, unlike the other biological macromolecules. T/F | T |
| what are lipids made of? how does this impact polarity? | consist mostly of nonpolar carbon-hydrogen bonds and a little bit of O, are thus hydrophobic |
| 3 groups of lipids & which have fatty acids | triglycerides, steroids, phospholipids. All have fatty acids |
| fatty acids | long chains of carbons attached to a carboxyl group at one end |
| saturated v. unsaturated fatty acid | saturated: single-bonded C chain with H bonded to all other sites; unsaturated: C chain with double-bonded C atoms in centre -> less H (double bond takes up H bonding sites) & a "kink" in the chain |
| triglycerides | aka fats, 3 fatty acids linked to 1 glycerol molecule. Each fatty acid is linked to glycerol via dehydration reaction. Mainly function as energy storage |
| phospholipids | 2 fatty acids & a phosphate group attached to glycerol. Most have 1 saturated fatty acid tail and 1 unsaturated tail. Phosphate group forms a negatively charged, polar 'head' and fatty acid chains form hydrophobic 'tail' |
| what happens when phospholipids are added to water? | they self-assemble into a phospholipid bilayer with hydrophobic tails pointing towards the interior and each other, polar heads facing outwards. |
| amphipathic | "dual property" - refers to molecules that have both hydrophilic and hydrophobic components |
| steroids | lipids characterized by a C chain consisting of 4 fused rings. Important steroid: cholesterol - component in animal cell membranes & precursor for some steroid hormones |
| plasma membrane | boundary that separates the living cell from its surroundings & compartments in cells. Exhibits selective permeability |
| selective permeability | capacity to cross; allowing some substances to cross it more easily than others - hydrophobic outside & interior hydrophobic region |
| mosaic of cell membrane | some proteins & carbs are part of membrane composition, making it a mosaic |
| describe fluidity of the cell membrane | the interactions between phospholipids are weak, they move in the membrane's plane. Thus, membrane is fluid & dynamic mosaic. Lipids rapidly move laterally, rarely flip-flop. Fluid to function, but not TOO fluid. |
| types of membrane proteins | peripheral proteins, integral proteins, transmembrane proteins. Types of proteins in the membrane mosaic determine most of membrane's specific functions, which differ based on cell type |
| peripheral proteins | on the membrane surface, ionic and H-bond interactions with hydrophilic lipid & protein groups, only in the hydrophobic region |
| integral proteins | possess hydrophobic domains which are anchored to hydrophobic lipids, partially in cell membrane |
| transmembrane proteins | span the membrane, hydrophilic & hydrophobic regions. Allow for the passage of hydrophilic things - can be enzymes, receptors, cell recognition, intracellular joining, cytoskeleton attachment to extracellular matric |
| why are flip-flops rare events in the movement of the phospholipids? | the ends are differing hydrophilic/hydrophobic - to flip-flip, the hydrophilic head hast to move into the hydrophobic region |
| describe carbohydrate function in cell membranes | carbs bond covalently in the membrane to proteins (form glycoproteins) or lipids (form glycolipids). On external side of membrane, carbs vary among species, individual and even cell types. Important in cell-cell recognition |
| what may effect membrane fluidity & permeability? | as fluid & dynamic mosaic, fluidity & permeability of membrane may change depending on its composition & the environment |
| cell membrane fluidity | the ability of molecules to move in the membrane/viscosity of the membrane. Affects the diffusion of proteins & other molecules inside cells, thus affecting their function. Fluidity is affected by phospholipid structure, cholesterol composition, & temp |
| cell membrane permeability | the rate of diffusion of molecules across the membrane/how easily molecules pass thru the membrane barrier. Fluidity can affect membrane permeability. Majorly impacted by transport proteins |
| cell membrane fluidity & temperature | as temperatures increase, membrane move from solid (gel) state -> move fluid state = increases permeability. Cold environment usually compresses membranes, makes them less fluid, less permeable & more susceptible to rupture |
| cell membrane & cholesterol | cholesterol regulates temp. as a buffer of fluidity in the cell membrane. Component of animal cell membranes. |
| chemical structure of cholesterol | Amphipathic: hydrophilic hydroxyl group and a hydrophobic region at 4 interconnected carbon rings. |
| cholesterol & cell membrane fluidity at normal (warm) temps | cholesterol decreases membrane fluidity by restraining the movement of phospholipids - prevents them from falling apart |
| cholesterol & cell membrane fluidity at cool temps | cholesterol increases membrane fluidity by preventing phospholipids from packing tightly - prevents membrane from getting dense & breaking |
| cell membrane fluidity & fatty acid chains: short vs long | shorter fatty acid chains in the phospholipids form a thinner membrane that is more fluid and more permeable, allowing faster diffusion. Longer fatty acid chains form a thicker membrane that interacts more and is less fluid. |
| cell membrane fluidity & fatty acid chains: saturated vs unsaturated | saturated fatty acid chains allow phospholipids in the bilayer to pack closely together, making a denser, less fluid & less permeable membrane. The kinks in unsaturated fatty acid chains create space between phospholipids and makes more fluid membrane |
| define selectively permeable | the cell membrane is permeable to/allows some substances to cross but not others |
| what makes the membrane selectively permeable? | phospholipid bilayer - hydrophobic (nonpolar) molecules pass thru rapidly; polar molecules/ions do not cross easily. AND transport proteins span the membrane & and specific to the solutes they can transport |
| channel protein | transport protein of the cell membrane that has a hydrophilic channel that certain molecules/ions can use as a tunnel to pass thru the membrane by passive transport |
| carrier protein | transport protein that binds to specific molecules and shuttles them across membrane by changing shape; may use active or passive transport |
| passive transport | movement of molecules across a selectively permeable membrane without the use of energy (by diffusion) |
| 3 types of diffusion & whether they move solute or solvent | simple diffusion - solute, facilitated diffusion - solute, osmosis - solvent (water) |
| what directly influences the rate of diffusion? | how steep the concentration gradient is (bigger difference between high & low concentration of sides = faster diffusion) |
| dynamic equilibrium | state of diffusion where solutes still move back and forth, but there is no net change in concentration on either side of the membrane |
| simple diffusion & what molecules use it | no transport protein involved. Usually small hydrophobic molecules ex. O2, CO2, CH3 |
| facilitated diffusion & what molecules use it | use transport proteins to speed up/down and/or allow movement of molecules across membrane. Small hydrophilic molecules/ions ex. glucose, Na+ |
| diffusion | net movement of particles from an area of high -> low concentration by the natural tendency and kinetic energy of the molecules to go from where they are more concentrated to where they are less concentrated. No energy use |
| osmosis | diffusion of water across a selectively permeable membrane |
| water diffuses before solutes across a membrane. T/F | F. If solutes cannot move across the membrane, water will move instead to reach dynamic equilibrium |
| describe water's movement by osmosis | water molecules move from region of lower solute concentration (higher water concentration) to higher solute concentration (lower water concentration) |
| how does water move across the phospholipid bilayer? | water moves either by simple diffusion (very, very slowly, because it is small enough to make it thru) or by facilitated diffusion thru aquaporins (channel proteins for water that significantly speed up its diffusion) |
| tonicity | total solute concentration in a solution; the ability of a solution to cause a cell to lose/gain water |
| isotonic | refers to two solutions that have equal solute concentrations |
| hypertonic | a solution that has a higher solute concentration than the other solution |
| hypotonic | a solution that has a lower solute concentration than the other solution |
| cell without a cell wall in isotonic, hypotonic & hypertonic solutions | iso: no net water movement across the cell membrane; normal state. Hypo: net water movement into the cell; cell lyses. Hyper: net water movement out of the cell; cell crenates/shrivels. |
| cell with a cell wall in isotonic, hypotonic & hypertonic solutions | iso: no net water movement; cell becomes flaccid. Hypo: net water movement into the cell; cell is turgid (normal). Hyper: net water movement out of the cell; cell plasmolyzes. |
| why do animal and plant cells behave differently in hypotonic solutions? | plant cells have a cell wall while animal cells do not. The rigidity of the cell wall allows plant cells to maintain their shape and resist the uptake of water in a hypotonic solution. |
| plasmolysis | a usually lethal effect where a cell's cytoplasm pulls away from the cell wall due to a large loss of water (hypertonic environments) |
| active transport & molecule examples | the movement of molecules against their concentration gradient; requires ATP. Important for the creation of concentration gradients. Uses carrier proteins. Ex. glucose, amino acids |
| bulk transport | large molecules/large quantities of small molecules actively transported across the membrane |
| exocytosis | membrane-bound vesicle from inside the cell fuses with the membrane and expels its contents to the outside; contents EXIT |
| endocytosis | membrane folds inward, trapping material outside for use inside the cell; contents ENTER |
| types of endocytosis | phagocytosis, pinocytosis, receptor-mediated endocytosis |
| phagocytosis | a cell engulfs a solid particle in a vacuole (eating) |
| pinocytosis | a cells uptakes fluids or very small particles in a vacuole (drinking) |
| receptor-mediated endocytosis | binding of ligands to receptors triggers vesicle formation; specific to one type of molecule |
| ligand | any molecule that binds specifically to a receptor site of another molecules |
Created by:
AntBanana
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